Spencer 2.0 kept up the recent tradition of relatively unheralded Braves prospects coming up and playing excellent ball nearly from the get-go
During their current competitive stretch, the Braves have benefited from huge rookie seasons from various members of their core. 2018 wouldn’t have been 2018 if not for the debut and general awesomeness of Ronald Acuña Jr., but he was already thought of as a phenom. The same goes for Michael Soroka, who gave us that one beautiful full season in 2019 before life got in the way. And then, after a brief hiatus, Michael Harris II and Spencer Strider came out from seemingly nowhere (certainly not, say, most Top 100 prospects lists) to dominate the league and save the 2022 season. The Braves didn’t need any rookie magic when firing on all cylinders in 2023, but come 2024… it was time for Spencer Schwellenbach to fly through the minor league system and save the day, and he did exactly that with aplomb.
How acquired
The Braves took Schwellenbach in the second round of the 2021 MLB Draft, 59th overall. A two-way player at Nebraska (the university, not like, just the state) that checked a lot of boxes the Braves have on their theoretical “likes” sheet, Schwellenbach went down with Tommy John Surgery shortly after joining the organization. He made it up to High-A last year, started there this year, and made just two starts in Double-A before getting the call to the big league roster.
What were the expectations?
Schwellenbach had such a limited track record in the minors that answering this question is tough. It’s also largely irrelevant: the Braves clearly promote players when they’ve met some kind of internal, not-viewable-in-surface-stats criteria, and Schwellenbach apparently met set criteria pretty quickly into the 2024 season, outside expectations be damned. That said, he was generally viewed as something between a backend starter and a really good bulk reliever guy, or a middle-of-the-rotation arm, depending on who you asked, and when exactly you posed the question.
2024 Results
Schwellenbach made 21 starts in the majors, steadily working every six days-ish with some “regular rest” and extended delays between starts thrown in after his debut on May 29. He compiled 2.6 fWAR in the process (a smashing 4.2 fWAR per 200 innings) and had a it’s-not-weird-so-it’s-kinda-weird line with an 80 ERA-, 83 FIP-, and 83 xFIP-, with an xERA and SIERA in pretty much that same tight range as well. There were no ghosts, no HR/FB shenanigans in either direction, nothing of the sort — just more-than-solid pitching from a 24-year-old rookie.
What went right?
Man, Schwellenbach was so good that it’s hard to keep things short, or even manageable. The young righty quickly grew into his bewildering, five-pitch arsenal (with a sinker as a rarely-used sixth pitch). His four-seamer isn’t much to write home about, but he has a hard slider and a hard cutter with different movement profiles, and a splitter with great drop. His curve doesn’t look great on paper, but it absolutely baffled hitters to the tune of a whiff rate north of 40 percent. Command-wise, the cutter and split were ahead of the slider and curve, though, in particular, the split-finger was especially gruesome with a whiff rate north of 46 percent and a .218 xwOBA-against — it was his fifth-most-used pitch, but you might see him bump that up as it definitely warrants more screen time.
Against righties, Schwellenbach mostly went curve-fastball with a cutter to keep guys off balance; righties had an xwOBA no better than .302 against any of the three pitches. Against lefties, there were far fewer sliders, but they had to contend with the curve and deadly split. The four-seamer was really ineffective against lefties (perhaps obviously so) and his attempt to jam lefties with the cutter didn’t really work, but the split and curve were so good it almost didn’t matter. I mean it did matter as Schwellenbach had a near-4.00 xFIP against lefties compared to a sub-3.00 mark against righties, but dominating when you have the platoon advantage to that extent covers up a lot of warts.
Schwellenbach had a bit of an adjustment period, by which I mean, his first three starts. He was really fastball-heavy in the first one, slider-heavy in the second, and curveball-heavy in the third; the sequences were a bit raw and some of his chase pitches were still a bit too easy to hit. Then, it looked like the switch flipped against the Tigers, and he started getting the chases and whiffs he wanted, and basically didn’t look back. From June 18 through August 27, a 12-start stretch, he had an absurd 31.4 percent strikeout rate, 4.5 percent walk rate, and a 76/71/68 line. Not bad for a rookie starter with the perhaps tall task of having to deal with mechanics not just for two or three offerings, but five that he used with regularity.
Schwellenbach’s coolest start? Probably him dominating the Mets on July 27 as part of a 4-0 victory. He posted an 11/0 K/BB ratio in that game, which was about the greatest tribute to his injured teammate and name-brother that he could come up with. In some ways, it’s kind of sad, because that outing had a 0.02 FIP and 1.32 xFIP, and it’s gonna be hard for him to top those numbers in the future. (Well, he actually had a better start by xFIP, but gave up a couple of homers in that one.)
That video actually gives you a good sense into why he was so deadly when things were working for him: if you can get swings on stuff you bury, you can eventually just pump in fastballs down the middle and batters will be so focused on not chasing the stuff that makes them look bad that they’ll get blown away in the zone.
What went wrong?
Perhaps it shouldn’t have been surprising, but Schwellenbach faded a bit down the stretch. In the aforementioned 12-start span, he had an outing with an xFIP- above 100 once. From September 1-onward, it happened in four of six outings, and the 93 xFIP- he posted against the Reds was worse than all but two starts in the 12-start stretch. The culprits were pretty similar to his adjustment period to the majors: too many fastballs, and stuff intended to get chases not buried enough to get whiffs. The good news is that Schwellenbach did rebound by dominating the Mets (again) in Game 161 (5/0 K/BB ratio in seven frames), but even with that outing, his strikeout rate sat at just around 17 percent in those games as compared to 31.4 percent in the 12-start stretch (and below 18 percent in his three-start adjustment period).
One of his worst starts of the year came in that September span, as the Blue Jays drubbed him with a couple of Spencer Horwitz homers while he posted just a 3/0 K/BB ratio in five innings.
Beyond that, though, there isn’t really anything else to say that could’ve gone better — he pitched with aplomb, and even the times he was in left in too long, the damage wasn’t really directly his fault (though the team probably should’ve had him out of the game by then anyway).
2025 Outlook
In brief, Schwellenbach’s ascent through the ladder of possibilities continues. He’s now projected for 2.7 WAR over 172 innings by Steamer, and 2.6 WAR over just under 150 innings by ZiPS. Those figures include some regression to the mean, for sure, but given his September struggles, it’s going to be on Schwellenbach to show that he can roll with the punches of a full major league season, including opposing teams’ advance preparation for his arsenal, and its sheer length.
Only injuries really slowed down the other Braves super-rookies — it’s Schwellenbach’s turn to try and maintain his awesome rookie performance level while staying on the field.